Extracorporeal blood circuits are use to move blood outside the body: blood is typically pumped through tubes and arterial and venous bubble traps of disposable tubing sets connecting the patient to a blood treatment unit, for instance a dialyzer mounted on a dialysis, or to a treatment unit of another type (hemofilter, ultrafilter, hemodiafilter, plasmafilter, etcetera) associated to a corresponding blood treatment machine.
Integrated solutions have been used to ease the machine set-up before treatment starts.
U.S. Pat. No. 4,263,808 discloses, a one-piece circuit that includes arterial and venous bubble trap chambers in which blood enters at entrances above the bottoms of the chambers and leaves near the bottoms of the chambers. Pressure in the chambers can be determined by transducers placed against impermeable latex membranes covering holes communicating with upper portions of the chambers.
U.S. Pat. Nos. 4,798,090 and 4,666,598 disclose a one-piece fluid flow chamber cassette that can be mounted against a supporting machine. The cassette has a flexible tube that extends from a sidewall and forms a loop that is symmetrical about a loop axis that is transverse to the sidewall so that the loop will be acted upon by a pump roller on the machine when the front wall is against the machine. The flexible tube is connected at one end to a chamber outlet at the bottom of the chamber and at the other end to the inlet of a flow passage in the cassette, which inlet is located at the same distance from the loop axis as the chamber outlet; the cassette has two chambers (arterial and venous chambers) and additional flexible tubes for connecting a dialyzer between the flow passage and the venous chamber; the outlet of the venous chamber is at the bottom of the venous chamber; and the inlets to the arterial and venous chambers enter the arterial and venous chambers at locations above the outlets of the chambers. In use with a dialyzer, blood from a patient flows through the arterial chamber, the pump loop, and the flow passage to the dialyzer, and from there through the venous chamber and back to the patient.
It is also known measuring haemoglobin concentration in the blood circuit of a dialysis machine: a known way of determining the concentration of haemoglobin in the red corpuscles during the dialysis treatment, by means of highly accurate measurements of an intrusive kind, which require the laboratory examination of blood samples.
Other dialysis machines enable non-intrusive measurements of the haemoglobin concentration to be made within the machine. The non-intrusive measurements made within the machine are less accurate than laboratory measurements, but have the advantage of being provided in real time in such a way that the operating parameters of the dialysis machine can be corrected instantaneously. Italian patent IT 1240489 discloses a method of measuring the haemoglobin concentration within the machine and in a non-intrusive way, by measuring the absorption of electromagnetic waves of the blood flowing in the arterial branch of the first circuit.
In order to implement this method a blood circuit, having an arterial line, a venous line and a bubble trap in the arterial line, also included a calibrated and rigid piece of transparent tube is rigidly engaged at the outlet of the bubble trap, upstream the connection to the dialyzer. This calibrated piece of transparent tube was designed to be received in an appropriate holder where an emitter and sensor operated to emit and then detect the absorption of electromagnetic waves.
U.S. Pat. No. 6,794,194 discloses another method for measuring the hemoglobin concentration in an extracorporeal blood circuit of a dialysis machine comprising the measurement of the values of absorption by blood of electromagnetic waves conveyed along a section of the said circuit; then the calculation of the hemoglobin concentration is made as a function of the values of absorption and the measured value of blood pressure, blood temperature and the rate of flow of the blood along the aforesaid section.
According to this method a rigid piece of calibrated and transparent tube also including a pressure transducer is interposed between the blood pump and the dialyzer in correspondence of the arterial line, in a position where an electromagnetic waves sensor and a pressure sensor both borne by the machine operate.
It is also known to use the measure of haemoglobin concentration as a parameter to control the fluid removal from blood. For instance the ultrafiltration rate can be controlled by measuring the blood haemoglobin concentration upstream the treatment unit and by keeping said haemoglobin concentration or a parameter function of haemoglobin concentration (such as the filtration factor within a range of acceptability during treatment.
Finally EP0467805 shows a blood treatment apparatus having an optical/electronic system comprising an LED diode and a photosensitive sensor capable of receiving the light radiation emitted by the LED and of providing a corresponding electrical signal. A circuit for processing this electrical signal is able to discriminate when in use a tube through which blood flows is placed between LED diode and sensor. The equipment is provided with a test circuit to check that the parts of the equipment itself are properly operating.